The present invention relates to a printed circuit board presser device of a drilling machine, and more particularly, to a printed circuit board presser device which improves an efficiency of drilling operation.
A conventional printed circuit board drilling machine includes, for example, an arrangement such as illustrated in FIGS. 12 and 13.
In the drawings, reference numeral 1 denotes a printed circuit board (which will be simply referred to as a "board", hereinafter). Reference 2 is an upper plate superposed upon the board 1. Reference 3 is a lower plate which is located below the board 1. Reference 4 designates locating pins fixed through the upper plate 2, the board 1 and the lower plate 3 and extending outwardly from the lower plate 3. Reference numeral 5 is an adhesive tape for securing the peripheral side portions of the upper plate 2, the board 1 and the lower plate 3.
The upper plate 2, the board 1 and the lower plate 3 are integrally connected with each other by the pins 4 and the adhesive tape 5, and an assembly including these components will be hereinafter referred to as a work W.
Reference numeral 6 designates a table supported on a bed, which is not shown, so as to be movable forward and rearward perpendicular to a paper sheet of the drawings. There is provided on that table 6 fixture means (not shown) for locating and securing the pins 4. Reference 7 is a feeder screw which is rotatably retained on the bed and is driven to rotate by a motor (not illustrated), to thereby displace the table 6. Reference 8 indicates a slider supported on a column movably in the rightward and leftward directions in the drawings, the column being not shown. Reference 9 indicates a feeder screw which is rotatably supported on the column and driven for rotation to move the slider 8 by a motor 10. Reference 11 is a saddle retained by the slider 8 vertically movably in the planes of the drawings. Reference 12 denotes a feeder screw which is rotatably supported on the slider 8 and driven for rotation by a motor to move the saddle 11. Reference numeral 14 is a spindle unit for receiving a rotatable spindle (not shown) therein and secured on the saddle 11. Reference 15 shows a ring in which a shank portion of a drill 16 is press-fitted.
Reference numeral 17 indicates cylinders which are supported on the saddle 11 and which position at the locations on the right and left sides of the spindle unit 14. Reference numeral 18 is a board presser device slidably fitted on the spindle unit 14 and supported by the cylinders 17.
This board presser device 18 is formed at its lower center with a hole through which the drill 16 can pass. An annular press-contact portion 18a for holding the work W is provided on the periphery of the hole. The press-contact portion 18a is formed at its lower end surface with grooves 18b for sucking air during drilling operation. Also, there is provided on the side surface of the board presser device 18, an aperture 18c for discharging chips produced by the drilling operation.
Reference numeral 19 designates a chip collector, and reference 20 is a pipe which connects the aperture 18c of the board presser device 18 to the chip collector 19 to each other.
Compressed air of a predetermined pressure is delivered to the cylinders 17 in order to force the board presser device 18 downwardly while the chip collector 19 is operated, thus discharging air within a space defined between the spindle unit 14 and the board presser device 18.
In this state, the table 6 and the slider 8 are moved to adjust a setting position of the drill 16 to a position of the board 1 to be drilled. Then, the motor 13 is made to drive so as to lower the saddle 11 for carrying out a drilling operation. More particularly, when the saddle 11 starts to descend, at first, the press-contact portion 18a of the board presser device 18 is brought into contact with the upper plate 2. Successively, when the saddle 11 further descends, the board presser device 18 presses the work W against the table 6 by the pressure of the compressed air supplied to the cylinders 17. When the saddle 11 still further descends, the drill 16 is protruded from the board presser device 18 to conduct the drilling operation. Concurrently, the chips produced from the drilled portion are discharged to the chip collector 19, carrying on a flow of air sucked from the groove 18b of the board presser device 18.